Gas-fired forced convection ovens

ABSTRACT

In the preferred form, the present invention concerns a gas oven having a cavity including a rear wall, a gas burner mounted on the rear wall, a flow former spaced forwardly of the rear wall so as to form a combustion chamber between the flow former and the rear wall, a cooking chamber forward of the flow former, a blower mounted immediately forward of the flow former which causes recirculative gas flow through the cooking chamber and aids the passage of combustion chamber gases from the combustion chamber around the peripheral edge of the flow former.

O United States Patent [151 3,698,377 Smith I 1 Oct. 17, 1972 GAS-FIREDFORCED CONVECTION 3,437,085 4/1969 Perry ..l26/2l A OVENS 3,590,8037/1971 Sauer ..126/2l A [72] Invent: Anthony Smith, Marlow Bottom3,626,922 12/1971 Borge .;..l26/21 A England Primary ExaminerCharles J.Myhre [73] Assignee: The Hoover Company, North Can- AttorneyAlfred C.Gross and James A. Wanner ton, Ohio ABS CT 7 T [22] Filed: May 7, 1971[5 1 1 RA In the preferred form, the present invention concerns [21]APPL 141,280 a gas oven having a cavity including a rear wall, a gasburner mounted on the rear wall, a flow former 52 vs. C]. ..126/2l Aspaced forwardly of the rear wall as to form a 51 int. Cl. ..A2lb l/26,F24 15/32 hush Chamber between the form" and the rear [58] Field ofSearch "126/19 R 21 R 21 A 39 C wall, a cooking chamber forward of theflow former, a v l26/273 blower mounted immediately forward of the flowformer which causes recirculative gas flow through the cooking chamberand aids the passage of combustion [56] References cued chamber gasesfrom the combustion chamber around UNITED STATES PATENTS the peripheraledge of the flow former.

3,384,068 5/1968 Perry et al. ..l26/2l A 5 Claims, 5 Drawing FiguresPATENTEnum 17 I972 SHEET 2 0F 2 FIG.

1 GAS-FIRED FORCED CONVECTION OVENS BACKGROUND OF THE INVENTION 1. Fieldof the Invention This invention relates to gas ovens and is concernedwith aconstruction in which combustion products are distributed aroundthe cooking cavity of the oven by a blower in order to obtain a moreeven temperature distribution than normally occurs in a conventional gasoven.

According to the present invention a gas oven has an oven cavity dividedby a flow former into a combustion lative gases during operation of theoven.

2. Description of the Prior Art Most known gas-fired forced convectionovens use a fire box external of and separate from the oven cavity andconnected thereto by a duct or use a heat exchanger to provide heat inthe cooking compartment. Both of these systems tend to be expensive,both in cost and space employed.

Another known form of the gas-fired forced convection ovens utilizes achamber in the rear of the oven to house a blower which forces airaround a gas burner chamber with the exhaust of the gas burner chamberbeing somewhat limited in size and location. This arrangement is taughtin US. Pat. No. 3,384,068 wherein the combustion products exhaust nearthe top of the chamber and the recirculating gases are removed from thebottom of the chamber, thus causing a temperature differential alongdifferent walls of the oven.

SUMMARY OF THE INVENTION According to the present invention, a gas ovenhas a walled oven cavity, a rotary blower mounted within the cavity inclose proximity to a flow former, a combustion chamber formed behind theflow former and having one or more gas flame ports disposed therein,.

the combustion chamber having a peripheral outlet defined by theperiphery of the flow former and the walls of the oven cavity, and theblower being arranged to induce a flow of combustion products from thecombustion chamber through the peripheral outlet.

Preferably, the blower is mounted on a driving shaft passing through theflow former and rear wall with the bearings and motor for the blowerbeing external of the cooking compartment. The flow former may besecured into an inwardly projecting portion of the rear wall of the gasburner and partially defines the combustion chamber. The flow former,blower, and burner arrangement induce a flow of combustion productsaround the periphery of the flow former so that hot gases pass forwardlyalong the side, bottom and top walls of the cooking compartment.

It is also an object of the present invention that the gas burner bemounted on the rear wall of the cooking compartment and is provided withprimary and secondary air inlets at atmospheric pressure. The flowformer is disposed between the blower and the gas burner so as toprevent a direct flow of air from the blower to the gas flame ports.

Furthermore, in the preferred form, the gas burner is annular in shapeand permits passage of the driving shaft for the blower to the rear wallof the cooling compartment. I

It is a further object of this invention to provide a gas burnerandblower arrangement which utilizes little of the internal volume of thecooking compartment and utilizes few parts so that it is inexpensive tobuild.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of adomestic gas oven which utilizes the present invention. FIG. 2 is across-sectional view of the oven of FIG. 1.

FIG. 3 is a cross-sectional view taken along the lines 3--3,of FIG. 2.

FIG. 4 is a partial cross-sectional view of a second embodiment of thepresent invention.

FIG. 5 is a cross-sectional view taken along the lines 5-5 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS I FIG. 1 shows a domestic oven1 having a cabinet 2 with a front door 3. The oven may be provided witha removable rack 4 upon which food may be placed in the oven. The ovenmay also be provided with suitable controls generally indicated at 5.

The preferred and most highly developed embodiment of the presentinvention is taught in FIGS. 2 and 3. As shown in FIGS. 2 and 3 the ovenis provided with an internal insulated top wall 10, insulated bottomwall 11, and insulated side walls 12. Also, as shown in FIG. 2, the ovenis provided with an insulated rear wall 13. These insulated walls, alongwith the door 3, define an oven cavity 14.

Forwardly spaced of the rear wall 13 is a vertical plate hereinafterreferred to as a flow former 15. The

flow formerlS is parallel to the rear wall 13 and along with the rearwall 13 defines a combustion chamber 16. In this embodiment, the flowformer 15 is provided with a forwardly facing flange l8 spaced from thewalls l0, l1, and 12. The portion of the oven cavity 14 located in frontof the flow former 15 is hereinafter referred to as a cookingcompartment 17.

Located within the combustion chamber 16 and mounted in the rear wall 13is a gas burner 20. In the preferred form, the gas burner 20 is annularin shape and has a central passageway 21, the purpose of which will belater explained.

Within the combustion chamber the gas burner is provided with aplurality of gas flame ports 22. Preferably, these flame ports 22 aredirected radially outwardly around the periphery of the gas burner.Feeding the gas ports 22 is a manifold 23. The manifold 23 and thus thegas flame ports 22 are provided with a combustible mixture of primaryair and gas from a supply through an inlet pipe 25. The supply is theusual venturi-bellmouth arrangement 26. Also located in the rear wall 13is a plurality of secondary air inlet ports 24 directed to provide anadditional air supply in the vicinity of the gas flame ports.

Located immediately forward of the flow former 15 is a blower 30. Theblower 30 in the preferred form is a centrifugal fan of the disc typewith a central inlet and radial outward flow. In the preferred form, aplate 31 is also provided immediately forward of the blower 30 and issupported by brackets 29. The plate 31 has a central opening 32.Bridging the central opening 32 is a blower guard 33 which permits thepassage of gases to the central inlet of the blower but prohibits thepassage of large items such as food or the users hands.

Spaced radially outwardly from the blower 30 is an oven flue 34. One endof the oven flue is located between the flow former l5 and the plate 31.The opposite end of the oven flue 34 is connected to a product dilutionchamber 35. The product dilution chamber is provided with a dilution airinlet 36 and a product outlet 37.

In order to drive the blower 30, the preferred form of the oven isprovided with a shaft 38 passing through the central passageway 21 ofthe gas burner 20 earlier defined. The gas burner 20 supports a bearing39 which is located rearwardly of the oven cavity 14. In this manner thebearing 39 is not affected by the hot combustion gases in the combustionchamber 16. Also mounted on the shaft 38 is a pulley 40 which is drivenby a belt 41 from a motor pulley arrangement 42.

In the preferred form, the flow former is also provided with a forwardlyfacing peripheral flange 18 as stated above. The flange 18 is spacedfrom the insulated walls 10, 11, and 12, thus providing a combustionproduct outlet from the combustion chamber 16 between the peripheralflange 18 and the walls of the oven cavity. Furthermore, the flange isspaced outwardly from the peripheral edge of the plate 31 to provide agas recirculation exhaust from the blower 30 between the plate 31 andthe flange 18. The recirculation flow and combustion gases are mixed andare directed forwardly along the oven cavity walls.

During operation of the oven a primary air and gas mixture formed in theventuri-bellmouth arrangement 26 passes through the inlet pipe 25 andthe manifold 23 to the flame ports 22 where it is burned in thecombustion chamber 16. Secondary air at atmospheric pressure passesthrough the secondary air inlet ports 24 to aid combustion in thechamber 16.

The products of combustion will exhaust form the chamber 16 through thepassageway between the flange 18 of the flow former l5 and the insulatedwalls of the oven cavity. At the same time, the blower 30 will berotated through the motor pulley and shaft arrangement described above.

The forced convection caused by the blower 30 will cause a relativelyeven temperature distribution throughout the cooking compartment 17 bygas recirculation from the center of the cooking compartment, throughthe blower central inlet, and then through the blower radial exhaust andalong the insulated walls of the cooking cavity. This gas flow will alsoaid the exhaust of the combustion products from the combustion chamber16 around the periphery of the flow former 15 since these combustionproducts and the recirculatory air flow from the blower both exhaust inparallel passageways defined by the flange 18.

Part of the gases in the oven will be exhausted through the flue 34 intothe product dilution chamber 35 where atmospheric air is providedthrough the inlet 36 to cool the oven gases prior to leaving the oventhrough outlet 37.

It is noted that the combination of the combustion products and therecirculatory gases first pass along the top, bottom and side insulatedwalls of the chamber in a forward direction and then reverse flow so asto be drawn in through the inlet of the blower. This provides evendistribution of heat along all the insulated walls of the oven cavity.This is particularly beneficial in ovens of the self-cleaning nature.

FIGS. 4 and 5 show a modification of the oven taught in FIGS. 2 and 3.In this embodiment the insulated back wall 13 is provided with a gasburner of slightly different construction than that shown in FIG. 2.However, the gas burner is again provided with the manifold 23 and aplurality of gas flame ports 22 annularly disposed within the combustionchamber 16. Also provided are the secondary inlet ports 24.

The blower 30 in this embodiment is centrally located within the cookingcabinet in front of the flow former 15. The blower is of the axial flowtype. Since the combustion products from the combustion chamber 16exhaust radially outwardly, the flow former 15 has been curved so as toinsure the axial air flow through the blower is transformed into aradial exhaust so as to aid in the sweeping of the combustion productsfrom the combustion chamber.

While a guard has not been shown in FIGS. 4 and 5, such a guard could beprovided so as to insure that the user does not insert either his handsor food into the blower. An oven flue 34 and product dilution chamber 35are also provided similar to that taught in FIG. 2.

In this second embodiment the burner is provided with a frusto-conicalportion 45 which supports the flow former l5 and also provides for abearing 39 for the fan shaft 38. In order to provide cooling for thebearing which is now within the oven cavity, air inlet ports 46 areprovided.

Since the hot combustion products are being removed radially outwardlyfrom the combustion chamber 16 due to the influence of the blower 30,the air inlet ports 46 will help to cool the hub portion. The shaft 38is again provided with the pulley arrangement so as to drive the fan.

It is noted that both of these embodiments utilize a peripheral exhaustfrom the combustion chamber and a parallel peripheral exhaust from theblower help draw the combustion products from the combustion chamber.These gases are mixed and then all walls of the oven chamber are sweptby hot gases. Furthermore, by having a peripheral opening, the exhaustfrom the combustion chamber can be of relatively large area.

It is also noted in both of these embodiments that the blower and burnerarrangement are located on the rear wall of the oven cavity and utilizevery little internal volume of the oven cavity. Furthermore, relativelyfew parts are utilized and thus insures a relatively inexpensivemanufacture.

The foregoing is but the preferred forms of practicing the presentinvention. The invention is not limited to the particular details ormodifications shown and described. It is, therefore, intended that theclaims below will cover all modifications which will occur to thoseskilled in the art and do not depart from the scope and spirit of theinvention.

What is claimed is:

1. A gas oven comprising oven walls including a rear wall defining anoven cavity, a gas burner in said rear wall, a flow former parallel toand spaced from said rear wall so as to define a combustion chambertherebetween, said flow former having a periphery spaced from said ovenwalls so as to form an outlet from said combustion chamber, a blowermounted parallel to and forward of said flow former, said blowercreating forced circulation of gases in said oven cavity, whereby saidforced circulation of gases aids the flow of combustion products fromsaid combustion chamber.

2. The gas oven of claim 1 wherein said periphery of said flow formerhas a forwardly extending flange, said flange cooperating with saidblower to provide forward air flow along said walls of said oven cavity,and said blower having a central inlet so as to draw gases from thecenter of said cavity.

3. The gas oven of claim 1 including a panel positioned parallel to saidflow former and forward of said blower, said panel having a centralopening aligned with said central inlet of said blower, and guard meansmounted on said panel so as to prohibit passage of large articlesthrough said central opening.

4. The gas oven of claim 1 wherein said blower is mounted on a shaftpassing through said back wall.

5. The gas oven of claim 4 wherein said gas'burner is centrally locatedon said back wall, said gas burner having a central passageway, andincluding a bearing mounted in said central passageway exterior of saidoven cavity, said shaft being mounted in said bearing.

1. A gas oven comprising oven walls including a rear wall defining anoven cavity, a gas burner in said rear wall, a flow former parallel toand spaced from said rear wall so as to define a combustion chambertherebetween, said flow former having a periphery spaced from said ovenwalls so as to form an outlet from said combustion chamber, a blowermounted parallel to and forward of said flow former, said blowercreating forced circulation of gases in said oven cavity, whereby saidforced circulation of gases aids the flow of combustion products fromsaid combustion chamber.
 2. The gas oven of claim 1 wherein saidperiphery of said flow former has a forwardly extending flange, saidflange cooperating with said blower to provide forward air flow alongsaid walls of said oven cavity, and said blower having a central inletso as to draw gases from the center of said cavity.
 3. The gas oven ofclaim 1 including a panel positioned parallel to said flow former andforward of said blower, said panel having a central opening aligned withsaid central inlet of said blower, and guard means mounted on said panelso as to prohibit passage of large articles through said centralopening.
 4. The gas oven of claim 1 wherein said blower is mounted on ashaft passing through said back wall.
 5. The gas oven of claim 4 whereinsaid gas burner is centrally located on said back wall, said gas burnerhaving a central passageway, and including a bearing mounted in saidcentral passageway exterior of said oven cavity, said shaft beingmounted in said bearing.